The best that can be said in the short term is that the last quarter of 2013 was marginally ahead of expectations, with PC shipments down by 9.8 percent over the previous year instead of the projected 10.1 percent. But down is still down, and IDC cites "competition from other devices and economic pressures" as the culprits behind the decline.

"Other devices" isn't hard to parse: Tablet and smartphone sales continue to poach from the PC market unabated. Even Apple's Macintosh hasn't been immune to the overall decline -- although given the Mac's relatively small slice of the PC pie, if its sales should regain momentum it will not do much for overall PC numbers. And the odds are more likely that users of older Macs who don't have demanding workloads will simply move to iOS devices rather than buy into the next generation of Macs.

"Economic pressures" isn't just about the sluggish economy, but issues like the way future PC sales revolve around the growth of emerging markets. The report cites such circumstances as "a void in public sector spending this year after huge education deals seen in India and Malaysia last year failed to materialize," and "tectonic changes in politics" in Indonesia and Thailand, as well as India.

When PC growth does stabilize around 2018, it's expected to flatten out at around a shrink rate of 0.2 percent annually. Mature markets (such as the United States, Japan, and Europe) will continue to shrink at around 2 percent annually, and the only sustained growth will be for portable PCs in emerging markets -- only 2.6 percent annually, at that.

All this implies that the PC market will continue to exist -- after all, many existing use cases for PCs (content production systems, for instance) have not been displaced by mobile technology. But barring some grand innovation that hasn't materialized yet -- perhaps some final fusion of the desktop and portable PC into a device that works equally well in both environments -- the PC market is destined to settle into maintenance mode, where the only movement will be in replacing existing systems, and not in expanding sales to emerging markets, where demand will most likely already be satisfied by mobile devices.